Re: UMIP and clearcpuid=

[Borislav Petkov]

On Wed, Jun 10, 2026 at 08:41:02PM +0000, Ronan Pigott wrote:
> My use case is playing Windows video games via Wine. For whatever reason,
> they like to use these instructions:
> 
>   $ journalctl -b -g umip -o cat --since=-5m
>   umip_printk: 117 callbacks suppressed
>   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications.
>   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: For now, expensive software emulation returns the result.
>   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: SGDT instruction cannot be used by applications.
>   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: For now, expensive software emulation returns the result.
>   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications.
> 
> I don't think I benefit from the UMIP protection or the emulation, so I'd

Question is, do you benefit from disabling the UMIP emulation. Any noticeable
game performance increase?

> rather just disable it. clearcpuid still works, but results in a tainted
> kernel etc:
> 
>   kernel: clearcpuid: force-disabling CPU feature flag: umip
>   kernel: !!! setcpuid=/clearcpuid= in use, this is for TESTING ONLY, may break things horribly. Tainting kernel.

Right, I don't think a tainted kernel would be a problem but yeah...

I still think that it would make sense to issue a big fat warning when
disabling UMIP so that people know.
 
> so I think a umip=no flag as originally proposed could be preferable. Would
> that be acceptable?

umip=disable or umip=off

I guess.

Other than that, I guess that's a valid use case I'd say. Let's see what the
others think.

Thx.

-- 
Regards/Gruss,
    Boris.

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